Department of Environmental Science – Section of Environmental

Microbiology and Biotechnology- Aarhus University – Denmark

Filippo Casadei1,2, Aimei Wang3*, Merete Edelenbos3, Heleen Bukman4 and Anders Johansen2

CONCLUSIONS/SUMMARYFungal growth rate was strictly dependent on temperature and medium. For all the three fungal species, different growth rateswere observed when growing on the two media, with faster growth on OM medium than on PDA. Volatile analysis showed that B.allii, as well as P. polonicum and A. niger (data not shown), produced VOCs that were not present in the OM medium background.VOC profiling may be a suitable method for early warning detection of storage diseases,

Filippo Casadei

filippo.casadei01@

gmail.com

7th June 2015 – III International Symposium on Postharvest Pathology 2015 Bari, Italy

MATERIAL AND METHODSMycelial radial distribution on solid PDA and OM medium wasused as a measure of growth. To evaluate the influence oftemperature and medium on the production of VOCs, 35 μl offungi spore suspension was inoculated on PDA and OM in 20 mlvials. Vials were placed at 4°C, 15°C and 25°C and VOC profilesrecorded after 9 days by SPME/GC-FID and GC-MS analyses.

The sporification of Penicillium polonicum is greatly influenced by

growth medium, here after 7 day of cultivation on PDA and OM medium.

OBJECTIVES

The aim of this study was to evaluate the effects of medium (PDA:potato dextrose agar; OM: onion medium) and temperature (4°C,15°C, 25°C) on growth and production of VOCs from Penicilliumpolonicum, Aspergillus niger and Botrytis allii, which are commonspoilage organisms on onions.

1Department of Territorial Ecology and Environment, Faculty of Sciences, Pavia University, via S. Epifanio 14, 27100 Pavia, Italy 2Department of Environmental Science, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark3Department of Food Science, Aarhus University, Kirstinebjergvej 10, DK-5792 Aarslev, Denmark4Bejo Zaden B.V., Trambaan 2a, NL-1749 CZ Warmenhuizen, The Netherlands

INTRODUCTIONOnions are lost during post-harvest storage due to water loss, sprouting and microbial spoilage. Detection of fungal infection is adifficult task often leading to heavy economical losses due to improper detection technology and timely action. The use ofvolatile organic compounds (VOCs) as an early-warning tool to detect deterioration of onion produce, related to proliferation offungal spoilage organisms, may be a solution for spoilage monitoring during storage.

Radial growth (mm) of A.niger on PDA and OM. Values are mean ± standard deviations (n=4)

The project: 'Strategies and technologies to reduce postharvest losses of potatoes and vegetables’ is funded by the Innovation Fund.

OMPDA

RESULTS – MYCELIAL GROWTHMycelial radial distribution was strongly influenced bytemperature and to some extend growth medium as shown herefor A. niger. In contrast to A. niger, P. polonicum and B. allii grewwell at 4°C (data now shown), which is close to the temperatureconditions at commercial storage facilities.

Propanoic acid ethyl-ester

Methyl propyl sulfide

(1Z)-1-(Methylsulfanyl)-1-propene

Dimethyl disulfide

OM background

RESULTS – VOC PROFILESAll the fungal isolates produced volatiles. Below isshown overlayed chromatograms of VOC profilesobtained by SPME/GC-FID from three replicates of B.allii cultures grown on OM at 15°C for 9 days. Non-inoculated OM background is also shown. Theindividual compounds was tentatively identified bycomparing with respective GC-MS data.

Days of

Incubation

4°C 15°C 25°C

PDA OM PDA OM PDA OM

3 -¹ - - - 7.83 ± 1.16 8.50 ± 1.95

5 - - 1.34 ± 0.51 1.34 ± 0.12 20.58 ± 0.42 24.34 ± 1.53

7 - - 9.50 ± 2.07 6.42 ± 1.53 23.50 ± 1.47 30.92 ± 2.72

10 - - 15.34 ± 1.05 13.75 ± 2.81 29.25 ± 0.82 n.d.

13 - - 21.83 ± 3.23 28.08 ± 6.07 38.08 ± 1.83 n.d.

16 - - 26.50 ± 0.00 36.08 ± 4.84 n.d. n.d.

20 - - 31.75 ± 1.47 39.18 ± 3.32 n.d. n.d.

24 - - 34.34 ± 1.23 41.58 ± 0.59 n.d. n.d.

24 - - 37.07 ± 0.82 n.d.² n.d. n.d.

¹no visibile growth; ²the fungal mycelium reached the entire petri plate.

PDA OM